Electric air circuit breaker



March 18, 1947. w. G. HARLow ELECTRIC AIR CIRCUIT BREAKER Filed April 13, 1944 //////1// Ilz,

IIIlIl-llllllll z5' 25 so 4 inventor I Winton C5. Harlcw,

His Attorney Patented Mar. 18, 1947 2,417,683 ELECTRIC AIR CIRCUIT BREAKER Winton G. Harlow, Upper Darby, Pa., assignor to General Electric Company, a corporation of New York Application April 13, 1944, Serial No. 530,912

(Cl. 20D- 147) 5 Claims.

My invention relates to electric switches, and more particularly to air circuit breakers of the load-break disconnecting switch type for an intermediate voltage rating such as 15,000 volts, capable of interrupting and eiliciently clearing load power circuits, and has for its principal object the provision of an improved arc chute for a circuit breaker of the aforesaid type that greatly increases the circuit interrupting ability. Speciiically my invention is an improvement in electric air circuit breakers of the type disclosed in United States Letters Patent 2,399,485, issued April 30, 1946, and assigned to the same assignee as the present application.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view of an air circuit breaker embodying the present invention and shown in the closed circuit position thereof; Fig. 2 is an elevational View, partly in section, of the arc chute of the circuit breaker shown in Fig. 1 embodying my invention; Fig. 3 is a sectional view taken on line 3-3 of Fig. 2; Fig. 4 is a top view, partly in section, of the arc chute of Fig. 2; Fig. 5 is a sectional view taken on line 5-5 of Fig. 2, and Fig. 6 is an exploded perspective view of the stationary arcing contact of my improved circuit breaker.

The air circuit breaker shown in Fig. 1 is adapted both to interrupt load currents (as well as low amperage magnetizing currents), and to disconnect the circuit generally in the manner of the air break disconnecting switch.

Referring now to Fig. 1, the circuit breaker comprises a pair of relatively fixed terminals indicated at I and II arranged to be interconnected in the normal closed circuit position by a main current-carrying contact member I2. The contact member I2 is formed as a double blade contact that is secured to and mounted on a rotatable insulating shaft I3 for pivotal movement with respect to the upper fixed terminal I0. An operati-ng handle Il is connected to the insulating shaft I3 for rotating the same and causing the contact member or blade I2 to move toward and away from the fixed terminal I0.

The upper terminal I0 has connected thereto a fixed contact structure including an arcing contact I5, best shown in Figs. 2 and 6, and main current-carrying finger-type contacts I6 arranged to be engaged by the blade I2 (Fig. 1). Also mounted on the fixed terminal is an arc extinguishing structure, generally indicated in Fig. 2 at I'I, comprising in the specific instance a narrow arc chute to be described in greater detail hereinafter. The arcing contact I5 is mounted Within the arc chute for coaction with a movable arcing contact I8 that is pivotally mounted on and carried by the main blade as indicated at I9 (Fig. 1), whereas the main current contacts I6 are disposed exteriorly of the arc chute at oppo site sides thereof as also indicated in Figs. l and 2.

The movable arcing contact I8 is operatively related to the main current carrying blade I2 so that when the handle I4 is rotated clockwise from the position shown in Fig. l to open the circuit breaker, the main contacts at I2 and I6 first part contact and move a predetermined distance toward open circuit position before parting of the arcing contacts occurs at I5 and I8. Since the arcing contact I8 is electrically connected to the blades I2 the circuit between the terminals will be opened at the arcing contacts rather than at the main contacts so that the arc to be extinguished is drawn within the arc chute Il where it attaches to the arcing horns and is extinguished as it moves into the baille structure of the arc chute I1 to be described hereinafter.

To this end the movable arcing contact I8 is latched so that it does not immediately or completely follow the blades l2 until the blades reach a certain position whereupon the latch is tripped by means associated with the blade, and spring biasing means which are stressed during the initial movement of the blade cause the movable arcing contact to snap away from its fixed contact I 5. Coincident with this operation a strong jet of air is directed substantially transversely of the arc stream at the arcing contact so as to drive the arc upward within the chute, thereby to facilitate the interruption of large as well as small current arcs.

The specific construction. of the latching means, spring biasing means and air jet producing means forms no part of the present invention. Preferably these elements are constructed in accordance with the disclosure in the above mentioned Letters Patent. 'I'he latching means comprises a toggle adapted to be held in the overcenter position by spring means 20. The upper end of the toggle is provided with a roller 2| which is adapted to engage a fixed catch 22 provided on either side of the arc chute II, best shown in Figs. 2 and 3. The spring biasing means for the arcing contact I8 is not shown in the drawing, but preferably comprises a coiled spring or the like associated with the axis IS about which the arcingV contact I8 pivots. The air jet producing means is generally indicated at 23 and is operated upon movement of the movable arcing contact I8 away from the stationary arcing contact I 5.

My invention is specifically concerned with a new and improved arc chute or arc extinguishing structure which comprises spaced side walls 24 and 25 composed of arc resisting material, such as asbestos board comprising a mixture of Portland cement and asbestos. each side wall having on the side facing the other wall a plurality of parallel fins 24 and 25', respectively. as best shown in Figs. 2 and 4. The ns 24' and 25' are preferably integral with the side walls which are joined and suitably clamped together at the ends 25 and 2l. Each of the ends is preferably closed by a suitable spacer member 28. The chute sides 24 and 25 with the spacer members 28 are suitably bolted together, as indicated at 29, and preferably a sheet of insulating material 30 is provided on the outside of each side wail and also clamped by bolts 29 to give increased strength to the arc chute so that shock or vibration will not cause destruction thereof. The fixed catch 22, referred to above, is preferably formed as an integral part of each insulating sheet 30.

The arrangement and spacing of the fins 24' and 25' is such that when the side walls 24 and 25 are clamped together the fins are spaced and interleaved with respect to each other in staggered relation so as to form a sinuous or zigzag passage 3I (Fig. 4), into which the arc drawn is driven and extinguished. Preferably the fins 24' and 25' do not extend throughout the entire length of the arc chute, but the lower portion of the arc chute as viewed in Fig. 2 has no fins so as to provide a narrow slot 32 (Fig. 3) within which the arc is drawn. Preferably the fins extend along more than 50% of the surface of side walls 24 and 25.

Referring now to Fig. 3, which shows a transverse section of the zigzag arc chute passage defined by the fins 24 and 25', the fins are shown as tapered toward the entrance of the arc chute where they terminate into the portion of the chute which defines the narrow slot 32, within which the arc is initially drawn. The tapering edge is preferably defined by a. curvilinear contour, as illustrated, with the angle defined by the intersection of the curved edges being an acute angle. In accordance with my invention, the fins 24 and 25' near the exhaust end of the arc chute which is the upper portion of the chute as viewed in Fig. 2, are rectangular in construction and the curvilinear portion thereof does not start until about the points 33 in Fig. 3, a substantial distance from the exhaust end of the chute such as at least one-quarter of the chute dimension. Furthermore, above points 33 the fins associated with one chute side wall abut the other chute side wall, as is clearly shown in Figs. 3 and 4. By "engage is meant that the parts are sufiiciently close so that for all practical purposes they are in actual engagement whereby with this arrangement the chute is effectively closed at the exhaust end in so as movement of the arc into the exhaust portion of the chute is concerned. At the same time. however. the spaces 34 shown in Fig. 4 between adjacent ns 24' and 25' allow free venting of the hot arc gases. I have found that if the finsv at the exhaust end of the chute are spaced from the opposite chute side wall by less than 3'; of an inch, which spacing might be produced by manufacturing tolerances, the chute is substantially closed at the exhaust end in that it prevents the arc from being blown into this portion of the chute and in fact from travelling into the chute above the points 33 of Fig. 3. which will hereinafter be referred to as the exhaust portion of the chute. It will be seen that as the arc moves into the baille portion of the chute the curvilinear shape of the bailies remote from the exhaust portion of the chute is such that the arc is continually lengthened and forced into intimate contact with the fins and chute sides so that it is effectively extinguished in the region between the entrance to the baille portion of the chute and the exhaust portion of the chute. which is effectively closed in so far as movement of the arc therein is concerned.

In accordance with my invention the stationary arcing contact I5 comprises a double U- shaped member as best shown in Fig. 6, the identical portions thereof being designated as I5a and I5b, respectively, each having a downwardly extending portion one end of which is suitably fastened to a bolt 35 which supports the arcing contact in a recess 35 formed in the arc chute side walls 24 and 25. The bolt 35 electrically connects the arcing contact I5 through conductor 31 with terminal I0. Double U-shaped arcing contact also includes an upwardly extending portion I5 which is in effect a double arcing horn. The ends of this double arcing horn I5 are fastened as by welding to a pin 38 which is adapted to lit into openings 39 in chute sides 24 and 25. The arcing contact I8 is adapted to move in the space between portions I5a and I5b of arcing contact I5 which may be conveniently formed of relatively heavy wire. The arcing contact also moves in the space between the double arcing horn portion I5 of arcing contact I5.

Since the current which enters the arcing contact I5 where it is fastened to bolt 35 flows downwardly through portions I5a and I5b and then upwardly in the horn portions I5', the ux generated by the downward flow of current in portions I 5a and I5b of stationary contact I5 tends to drive the arc in a downward direction which is undesirable. Accordingly I provide the portions I 5a and I5b with ux shields 40 which comprise semi-cylindrical members having one end thereof welded or otherwise suitably fastened to washers 40. These washers are adapted to be slipped over bolt 35 thereby holding the flux shields in place. The flux generated by the current flowing upwardly in the arcing horn portions I5' will therefore be the only flux affecting the arc and will cause the arc to rise to the top of the arcing horn.

In order to accommodate the ux shields 40 chute side walls 24 and 25 are provided with an additional recess 4I within recess 38.

I have provided an arcing horn 42 identical in every respect with the stationary contact in arcing horn I5. described above, for the other side of arc chute I'I This arcing horn 42 is mounted in a recess 36 identical with the recess 35 described heretofore. The stationary contact I8 is adapted to move in the space between the double U-shaped members forming arcing horn 42 so as to literally wipe the arc off from arcing contact I8 onto arcing horn 42 whereupon the iet of air from the jet producing means 23 will force the arc into the baille portion of arc chute I1.

It should be understood that the chute side walls 24 and 25 having the integral fins 24 and 25 respectively, might be machined from asbestos board or might be molded from a suitable asbestos compound, In the event that the chute side walls were molded two recesses 36 and 42 would be molded in each side wall whereby the two chute side walls 24 and 25 would be identical and interchangeable.

In accordance with the disclosure of Boehne Patent 2,270,723, assigned to the same assignee as the present application, the side walls of arc chute l1 defining the narrow slot 32 of Fig. 3, are given a llame treatment thereby driving the moisture out of the chute and breaking up the surface bre structure of the material so as to prevent moisture from subsequently readily passing through the glazed surface. This flame treatment improves the dielectric qualities of the chute and acts otherwise in a useful manner. I have discovered, however, that when the current to be interrupted is low, as for example of the order of normal load, the interrupting ability and operating life are increased by omitting the llame or glazing treatment from the ns 24 and 25 in the upper portion of the arc chute. In accordance with my invention, the flame treatment, therefore, is given only in the throat portion up to a point such as is indicated by the broken line 43 in Fig. 2 although it may continue a moderate distance up the fins 24 and 25 with some reduction in effectiveness. The preferred treatment, therefore, results in an arc chute which is coated in its throat portion, with a glaze consisting of the fusion products of the chute material such as Portland cementasbestos fusion products, but which leaves the ns 24 and 25 free to absorb moisture and give it oil again. in the presence of an arc, to assist in the interruption of the arc.

From the above discussion it will be observed that I have provided a new and improved arc chute which is simple and inexpensive and which provides greatly increased circuit interrupting ability.

Although I have disclosed a particular embodiment of my invention, it will be obvious to those skilled in the art that modications may be made without departing from my invention and I intend in the appended claims to cover all such changes and modifications as fall Within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric air circuit interrupter comprising relatively movable contacts between which an arc may be formed upon opening of the circuit, and an insulating arc chute into which said are is driven comprising spaced side walls, each side wall having on its side facing the other wall a plurality of ridges extending longitudinally in the general direction of movement of said arc through said chute, the ridges of one wall being closely adjacent to, overlapping and staggered with respect to the ridges of the opposite wall so that the arc in passing through said chute is forced to take a tortuous closely conned path around the outer edges of said ridges to increase the length of and attenuate said arc, said ridges associated with each side wall at the exhaust portion ol said chute abutting the other side wall so as to interrupt the continuity of said tortuous arc path at the outer edge of each ridge over a predetermined portion of the chute whereby to prevent the travel of the arc into this portion of the chute.

2. An electric air circuit interrupter comprising relatively movable contacts `between which an arc may be formed upon opening of the circuit, and an insulating arc chute into which said arc is driven comprising spaced side walls, each side wall having on its side facing the other wall a plurality of ridges extending longitudinally in the general direction of movement of said arc through said chute, the ridges of one wall being closely adjacent to, overlapping and staggered with respect to the ridges of the opposite wall so that the arc in passing through said chute is forced to take a tortuous closely confined path around the outer edges of said ridges to increase the length of and attenuate said arc, said ridges associated with each side wall at the exhaust portion of said chute abutting the other side wall so as to interrupt the continuity of said tortuous arc path at the outer edge of each ridge whereby to prevent the passage of the arc past said abutting edges.

3. An electric air circuit breaker comprising relatively movable contacts between which an arc may be formed upon opening of the circuit, and an insulating arc chute into which said arc is driven comprising spaced side walls, each side Wall having on its side facing the other wall a plurality of ridges extending longitudinally in the general direction of movement of said arc through said chute, the ridges of one wall being closely adjacent to, overlapping and staggered with respect to the ridges of the opposite wall so that the arc in passing through said chute is forced to take a tortuous closely confined path around the outer edges of said ridges to increase the length of and attenuate said arc, said ridges associated with each side wall at the exhaust portion of said chute abutting the other side wall so as to interrupt the continuitj7 of said tortuous arc path at the outer edge of each ridge over a predetermined portion of the order of one quarter of the chute measured from the exhaust end of the chute whereby to prevent travel of the arc into this portion of the chute.

4. An electric circuit interruptor comprising a pair of relatively movable contacts between which an arc is drawn upon separation of said contacts, an arc chute associated with said contacts, one of said contacts being a stationary contact mounted within said arc chute, said stationary contact comprising a cylindrical rod of U-shaped configuration with the base of the U extending downwardly in said arc chute, means for supporting said contact in said arc chute at the upper end of one of the legs of said U, the other of said legs of said U forming an arcing horn, means for connecting an associated electric circuit to said contact at the upper end of said one leg, and ux shielding means for substantially enclosing said one leg of said U comprising a pair of semi-cylindrical members formed of magnetic material.

5. An electric circuit interrupter comprising a pair of relatively movable contacts between which an arc is drawn upon separation of said contacts, an insulating arc chute associated with said contacts, one of said contacts being a stationary contact mounted within said arc chute, said stationary contact comprising a heavy wire of adouble U-shaped configuration with the base of the U extending downwardly in said are chute, the other of said contacts being movable to engage both portions of said double U-shaped contact, means for supporting said contact in said arc chute at the upper end of one of the legs of said U, the other of said legs of said U forming an arcing horn, and means for connecting an associated electric circuit to said Contact at the upper end of said one leg.

WINTON G. HARLOW.

REFERENCES CITED The following references are of record in the me of this patent:

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